1. Field of the Invention
The present invention relates to a wire clamping device and wire clamping method used to clamp bonding wires in the wire bonding of electronic components.
2. Description of the Prior Art
In semiconductor devices and other electronic components, gold, aluminum and other types of bonding wire are generally used to bond the pad (electrode) of the pellet and the substrate. An example of a wiring bonding apparatus used in wire bonding is shown in FIG. 4. This wiring bonding apparatus is used to bond a substrate 6 and a pellet 5 of a semiconductor device. Said wire bonding apparatus has a positioning table 7 on which the substrate 6 is placed and a bonding head 9 which is moved in the X and Y directions (horizontally) with respect to said positioning table 7. Said bonding head 9 is moved horizontally by the X-Y drive section 8. The bonding head 9 supports the bonding arm 10 in a horizontal state so it can move up and down. The end of said bonding arm 10 is positioned above the substrate 6 placed on the positioning table 7, and a bonding tool 11 is attached to the end of the bonding arm 10. Above the bonding arm 10, a wire clamping device 14 is supported by the end of the clamping device support arm 13 which is in a horizontal state. Said wire clamping device support arm 13 is attached to the bonding head 9 and can move up and down. The wire clamping device 14 clamps the vertical wire 4 unwound off the wire spool 12 above the bonding head 9.
Wire bonding is performed by this wire bonding device as described below. After the substrate 6 is placed on the positioning table 7 and positioned, the X-Y drive section 8 drives the bonding head 9 in the X-Y directions. This causes the bonding tool 11 to move above the pellet 5 on top of the substrate 6 so the end of the bonding tool 11 and said pellet 5 oppose each other. While in this state, the bonding arm 10 comes down. This causes the bonding tool 11 to press the wire 4 against the pad of the pellet 5, and the wire 4 is bonded to the pad of the pellet 5. The bonding arm 10 rises after the wire 4 is bonded to the pad of the pellet 5.
The bonding head 9 is then moved in the X-Y direction by the X-Y drive section 8, and the bonding tool 11 moves above the substrate 6. This moves the end of the bonding tool 11 so it opposes the post of the substrate 6 where there is no pellet 5. The movement of the bonding tool 11 at this time unwinds wire from the wire spool 12. In this state, the bonding arm 10 comes down and the wire 4 is pressed against and bound to the post of the substrate 6 by the bonding tool 11.
When the pad of the pellet 5 and the post of the substrate 6 are connected by the wire 4 in this manner, the wire clamping device 14 operates and clamps the perpendicular wire 4. The clamping device support arm 13 then rises and the wire clamped by the clamping device 14 is cut away from the post of the substrate 6 to which it was bonded by the bonding tool 11.
The wire used in wire bonding generally ranges from several microns to several tens of microns in diameter.
The wire clamping device 14 used on this kind of wire bonding apparatus generally has the structure shown in FIG. 5. Said wire clamping device 14 has a pair of parallel arms 19 and 20. The end of each arm 19 and 20 oppose each other, and the perpendicular wire 4 passes between them. The arm 20 is fixed and the end of the other arm 19 is in contact with the end of the plate spring 18, and said plate spring 18 causes the end of the arm 19 to move near the end of the fixed arm 20. When the end of the movable arm 19 is moved toward the end of the fixed arm 20 by the plate spring 18, the perpendicular wire 4 positioned between the ends of the two arms 19 and 20 is clamped by the ends of the two arms 19 and 20.
The base of the plate spring 18 is linked to the lever 16, which is capable of rotating, through the rotating member 17, which is also capable of rotating. Said lever 16 is linked to the solenoid 15, and the lever 16 is rotated by driving the solenoid 15. The rotation of the lever 16 causes the rotating member 17 to rotate, which in turn causes the end of the plate spring 18 to move the end of the movable arm 19 toward the end of the fixed arm 20.
In the wire clamping device 14 with this configuration, the movable arm 19 is moved and clamps the wire 4 by activating the solenoid 15, and clamping is released by deactivating the solenoid 15. Therefore, the clamping force on the wire 4 remains fixed and cannot be changed. As a result, if a wire 4 with a different diameter is to be clamped, the wire 4 cannot be clamped with a suitable clamping force. Further, there are many parts and the structure is complicated, so assembly, adjustment and maintenance are difficult and response is poor.